Standards Publication No

STANDARDS PUBLICATION NO. MFMA-4

METAL FRAMING

STANDARDS PUBLICATION

2004 Revision

Metal Framing Manufacturers Association 2004

$5.00

FORWARD

This Standards Publication provides practical information concerning the design, test, and manufacture of metal framing (continuous slot metal channel systems). It provides guidelines for the manufacture of reliable products.

This Standards Publication represents the results of years of research, investigation, and experience by the members of the Metal Framing Manufacturers Association (MFMA). It has been developed through continuing consultation among manufacturers, users, and national engineering societies and is intended to improve serviceability and safety.

This Standards Publication addresses the design, test, and manufacture of Metal Framing System components over which the manufacturer has control. The safety of the total system also involves the system designer, installer, and user. The manufacturer has limited or no control over factors such as: environmental conditions, total system design, product selection and application, installation practices, and system maintenance. Consequently, MFMA disclaims all warrantees, express and implied, associated with this Standards Publication. This Standards Publication has been developed with a view towards promoting safety to persons and property when the Metal Framing System is properly selected, used, and installed according to Article 384 of the National Electrical Code. The products referenced in this publication normally comply with the requirements of Underwriters Laboratory Standard UL5B.

This Standards Publication has been developed in the public interest and is intended to promote a better understanding between the manufacturer and the purchaser. It is intended to assist the purchaser in selecting and obtaining the proper product for a particular need. This is a voluntary standard and does not, in any respect, preclude any member or non-member from manufacturing or selling products not conforming to the standard.

This Standards Publication will be reviewed and updated periodically. MFMA will continue to welcome written comments from interested parties at any time. All such comments should be addressed to:

Mr. Jack M. Springer, Executive Director

Metal Framing Manufacturers Association

401 N. Michigan Avenue

Chicago, IL 60611-4267

Phone: 312.644.6610
Fax: 312.321.4098
For more information, please contact:

SCOPE

The requirements given in this publication apply to design, test, and manufacture of ferrous and nonferrous metal framing (continuous slot met channel systems) which consist of channels with in-turned lips and associated hardware for fastening to the channels (Strut) at random points.

FORWARD-i-

SCOPE-ii-

SECTION 1DEFINITIONS1

SECTION 2DESIGN DATA3

Structural Design3

Dimensional Data3

Channel Properties3

Maximum Design Stress4

Load Tables4

Safety Factors5

Application Data5

SECTION 3MATERIALS6

Channel6

General Fittings and Accessories6

Fasteners7

SECTION 4FINISHES8

Metallic Coatings8

Nonmetallic Coatings9

Combination Coatings9

Underwriters Laboratories Listed Items9

SECTION 5TOLERANCES10

Channel, Steel (Roll-Formed)10

Channel, Aluminum (Extruded)12

Fittings and Accessories, Steel and Aluminum (Fabricated)14

Fittings and Accessories, All Sand Cast Metals14

Fittings and Accessories, All Die Cast Metals14

SECTION 6FASTENERS AND THREADS15

SECTION 7WELDING16

SECTION 8MARKING17

Channel and Closure Strip17

General Fittings, Accessories, and Fasteners17

Steel Straps for Copper Tubing17

Underwriters Laboratories Marking17

Alternate Marking Requirements17

iii

SECTION 9TESTING AND INSPECTION18

Testing – General Fittings, Accessories, and Hardware18

Slip Test on Channel Nut19

Pullout Test of Channel Nut20

Pullout Test – Clamp (Strap) From Channel21

Slip Test – Clamp (Strap) Along Channel23

Slip Test – Conduit, Pipe, or Tubing Through Clamp (Strap)24

Fitting Load Test26

Cantilever Load Test28

Concrete Insert Pullout Test29

Inspection30

APPENDICES

A – BIBLIOGRAPHY OF SOURCES-v-

B – MEMBER COMPANIES –

METAL FRAMING MANUFACTURERS ASSOCIATION-vi-

SECTION 1

DEFINITIONS

1.1CHANNEL (STRUT)

The term channel (strut) as used within this standard refers to continuous slot channel (strut) with inturned lips. Multiple channel configurations can be fabricated from single channels.

PROFILE OF TYPICAL METAL FRAMING CHANNEL

Figure 1

1.2CHANNEL NUT

Channel nuts are designed to provide a secure means of attachment when positioned in the continuous slot of a channel.

The nut is formed or stamped in a way that resists slipping along the channel lips after tightening. See Figure 2.

TYPICAL CHANNEL NUTS

Figure 2

1.3CONCRETE INSERT CHANNEL

A concrete insert channel is a channel having formed or attached anchors, which will support the insert within hardened concrete. This provides means for attachment at random points along the continuous slot.

1.4ELECTRICAL ACCESSORIES & FITTINGS

Electrical Accessories & Fittings are those items that:

a.)facilitate the use of metal framing channel as electrical raceways and/or,

b.)are utilized to attached, support, or hang electrical materials to or from metal framing components.

1.5ELECTROPLATING

In this process a ductile coating of zinc is applied by electro-deposition.

1.6FASTENERS

Fasteners consist of items such as screws, bolts, hex and square nuts, washers, and lock washers. Channel nuts are defined under 1.2.

1.7GENERAL FITTINGS

General fittings are those which are attached to channels to form a rack, frame, or continuous run of channel.

1.8HOT DIP GALVANIZING AFTER FABRICATION

In this process, a zinc coating is applied to a cleaned and fluxed surface by dipping into a molten zinc solution. Hot dip galvanizing after fabrication is performed on steel framing and system components after all cold working, cutting, punching, or welding is complete.

1.9IN LINE HOT GALVANIZING

In this process, a molten zinc solution is deposited on a cleaned surface in a continuous manner during the cold forming operation.

1.10MECHANICAL ACCESSORIES & FITTINGS

Mechanical accessories & fittings are those items used to support, attach, or hang materials for plumbing, heating, cooling, power, and process piping.

1.11MILL GALVANIZED BEFORE FABRICATION OR PRE-GALVANIZING

“Mill galvanizing” or “Pre-galvanizing” is the application of zinc on steel sheets or coils in a continuous hot dip process prior to cold working, cutting, punching, or welding of the steel.

SECTION 2

DESIGN DATA

2.1STRUCTURAL DESIGN

Metal framing structural supports shall be designed in accordance with the following standards:

a)AISI “Specification for the Design of Cold-Formed Steel Structural Members”, latest edition.

b)The Aluminum Association “Aluminum Construction Manual, Section 1, Specifications for Aluminum Structures”, latest edition.

2.2DIMENSIONAL DATA

Dimensional data for channel and fittings published by the manufacturer should include:

a)Material thickness

b)Length

c)Width

d)Depth

e)Size or location – holes and slots

f)Thread sizes

g)Concrete inserts – anchor type, size, and spacing

2.3CHANNEL PROPERTIES

The manufacturer’s design data for channels should include:

a)Moment of inertia (I) – xx and yy axis

b)Section modulus (S) – xx and yy axis

c)Radius of gyration (r) – xx and yy axis

d)Cross sectional area of channel

e)Weight per foot

The moment of inertia (I), section modulus (S), radius of gyration (r), and cross sectional area of channel shall be based upon the full cross section of the channel (or net section when applicable), except when the use of a reduced cross section is required by the AISI “Specification for the Design of Cold-Formed Steel Structural Members”, latest edition.

The uncoated minimum steel thickness of the cold formed channel, as delivered, shall not be less than 95% of the thickness used in its design; however, thickness may be less at bends such as corners due to cold forming effect.

2.4MAXIMUM DESIGN STRESS

2.4.1The maximum design stress, in bending, recommended for metal framing sections formed from low carbon steel (0.25% or less), is 25,000 pounds per square inch (PSI). This is based upon a virgin steel minimum yield stress of 33,000 PSI cold worked to an average yield stress of 42,000 PSI.

2.4.2The maximum design stresses of aluminum sections will be found in the Aluminum Association “Aluminum Construction Manual, Section 1, Specifications for Aluminum Structures”, latest edition.

2.4.3In some applications, reductions in the maximum recommended design stress may be required by applicable standards and/or codes which govern the design for that particular application. Examples of these standards can be found in sub-sections 2.1 and 2.7.

2.5LOAD TABLES

2.5.1Beams & Columns

Load data published by the manufacturers for metal framing beams and columns shall be based upon calculations and should include:

a)Maximum uniform load on a laterally braced simple span as permitted by the design procedures in the AISI “Specification for the Design of Cold-Formed Steel Structural Members”, latest edition.

b)Uniform load on a laterally braced simple span that causes a deflection equal to 1/240 multiplied by the length of the span in inches, provided the load does not exceed that computed in item ‘a’.

c)Maximum deflection caused by the beam loading computed in item ‘a’.

d)Maximum axial load on columns as permitted by the design procedures in the AISI “Specification for the Design of Cold-Formed Steel Structural Members”, latest edition.

2.5.2General Fittings, Accessories, and Fasteners

Load data published by the manufacturers for general fittings, accessories, and fasteners shall be based upon tests of standards products and should include:

a)Slip resistance of channel nuts in continuous slot opening.

b)Pull-out resistance of channel nuts in continuous slot opening.

c)Bracket load data.

d)Fitting and accessory load data, where applicable.

e)Concrete insert pullout load data.

2.6SAFETY FACTORS

2.6.1The manufacturer’s published data for maximum design load will normally include a safety factor. The safety factor, unless otherwise noted, is the ratio of the ultimate load to the maximum design load.

2.6.2For static loads, a minimum safety factor of three (3) is recommended. In addition, harmful distortion of a particular component or assembly should not occur at a load less than the maximum design load multiplied by 1.68.

2.6.3For some applications, increases in the minimum safety factor may be required by applicable standards and/or codes, which govern the design of that particular application. Examples of these standards can be found in Sections 2.1 and 2.7.

2.7APPLICATION DATA

2.7.1Electrical Data

2.7.1.1Metal framing for use as an electrical raceway shall meet the requirements of:

a)Underwriters Laboratories, Inc. “Standard for Strut-Type Channel Raceways and Fittings”, UL5B.

b)“National Electrical Code”, ANSI/NFPA 70- NEC Article 384

2.7.1.2Electrical data published by the manufacturer should include:

a)Underwriters Laboratories, Inc. listing information, including conductor fill and cubic inch capacity of outlet boxes.

b)Knockout size and spacing.

2.7.2Piping Support Data

Where applicable, systems used to support piping should be designed in accordance with the American National Standard Code for Pressure Piping “Power Piping”, ANSI/ASME B31.1.

SECTION 3

MATERIALS

3.1MATERIALS

The material used in the manufacture of metal framing systems shall meet the requirements of the following Standards as applicable.

This specification is intended to cover ferrous and nonferrous base materials. Materials used in finishing, coating, and other secondary processes shall be addressed in specific specifications. Material specifications include, but are not limited to the following:

3.1.1Channel*

ASTM A167Stainless and Heat Resisting Chromium-Nickel Steel Plate, Sheet and Strip.

Same line, two different revisions:

ASTM A240/A240MHeat-resisting Chromium and Chromium-Nickel Steel Plate, Sheet and Strip for Fusion Welded Unfired Pressure Vessels.

ASTM A240/A240MHeat-resisting Chromium and Chromium-Nickel Steel Plate, Sheet and Strip Pressure Vessels.

ASTM A1008/Steel, Carbon, Cold-Rolled Sheet, Commercial Quality

A1008M

ASTM A366/Steel, Sheet, Carbon, Cold-Rolled, Commercial Quality

A366M

ASTM A1011/Steel, Carbon (0.15 maximum percent), Hot-Rolled Sheet and A1011M Strip Commercial Quality.

ASTM A1011/Steel, Sheet and Carbon-Stripped, Hot-Rolled, Structural

A1011MQuality.

ASTM A1008/Steel, Sheet, Carbon, Cold-Rolled, Structural Quality.

A1008M

ASTM A653/Steel, Sheet, Zinc-Coated (galvanized) by the Hot-Dip Process.

A653M

ASTM A659/Steel, Carbon (0.16 maximum to 0.25 maximum percent), Hot-

A659MRolled Sheet and Strip, Commercial Quality.

ASTM B209Aluminum and Aluminum-Alloy Sheet and Plate.

ASTM B221Aluminum, Aluminum-Alloy and Extruded Bar, Rods Wire, Profiles and Tube.

*Material standards for channels shall meet the requirements of paragraph 2.4.

When verification of minimum yield stress, before cold-working is required, certification shall be made by one of the following:

a)Steel supplier certified material test report (CMTR).

b)Metal framing manufacturer’s certificate of compliance (C of C) based upon two coupons per heat tested in accordance with ASTM A370-87c.

3.1.2General Fittings and Accessories

ASTM A36/A36MCarbon, Structural Steel.

ASTM A47/A47Ferritic Iron Castings.

ASTM A47/A47MCastings, Iron, Ferritic Malleable

ASTM A48/A48MGray Iron Castings.

ASTM A108Steel Bars, Carbon, Cold-Finished, Standard Quality.

ASTM A167Stainless and Heat Resisting Chromium-Nickel Steel Plate, Sheet and Strip.

ASTM A240/Heat-Resisting Chromium and Chromium-Nickel Stainless Steel

A240MPlate, Sheet and Strip for Pressure Vessels.

ASTM A242/High-Strength, Low-Alloy Structural Steel.

A242M

ASTM A653/For Zinc, Iron-Alloyed Coated.

A653M

ASTM A536Ductile Iron Castings.

ASTM A1011Steel, Carbon (0.15 maximum percent), Hot-Rolled Sheet and A1011M Strip, Commercial Quality.

ASTM A1011/Steel Sheet and Strip, Carbon, Hot-Rolled, Structural Quality.

A1011M

ASTM A575Steel Bars, Carbon, Merchant Quality, M-Grades.

ASTM A576Steel Bars, Carbon, Hot-Rolled, Special Quality.

ASTM A635/Steel Sheet, Strip, Heavy Thickness Coil, Carbon, Hot-Rolled.

A635M

ASTM A659/Steel, Carbon (0.16 minimum to 0.25 maximum percent), Hot-

A659MRolled Sheet and Strip, Commercial Quality.

ASTM A675/Steel Bars, Carbon, Hot Wrought, Special Quality, Mechanical

A675MProperties.

Add: ASTM A1018/Steel, sheet and strip, heavy thickness coils, hot rolled,

1018M carbon, structural.

ASTM B26/B26MAluminum-Alloy Sand Castings.

ASTM B85Aluminum-Alloy Die Castings.

ASTM B86Zinc-Alloy Die Castings.

ASTM B783Materials for Ferrous Powder Metallurgy (P/M) Structural Parts.

3.1.3Fasteners

SAE J429Mechanical and Material Requirements for Externally Threaded Fasteners.

SAE J995Mechanical and Quality Requirements for Steel Nuts.

ASTM A307Carbon Steel Bolts, Studs, 65,000 PSI Pencil Straight, Externally Threaded Fasteners.

ASTM A563Carbon and Alloy Steel Nuts.

ANSI B18.6.2 Slotted Head Cap Screw, Square Head Set Screw, and Slotted Headless Set Screws.

ANSI B18.6.3 Machine Screws and Machine Screw Nuts.

ANSI B18.21.1Lock Washers.

ANSI B18.22.1Plain Washers.

SECTION 4

FINISHES

4.1Framing channel, general fittings, accessories, and hardware may be manufactured with bare metal surfaces or with protective coatings as detailed in the sections below.

4.1.1Metallic Coatings

a)Electroplated Coatings

Framing channel, general fittings, accessories, and fasteners shall be electroplated in accordance with the following:

ASTM B633“Electrodeposited Coatings of Zinc on Iron and Steel.”

b)Hot Dip Galvanized After Fabrication

Framing channel, general fittings, accessories, and fasteners shall be hot-dip galvanized in accordance with one of the following:

ASTM A123/Zinc (Hot-Dipped Galvanized) coatings on Iron and

A123MSteel products.

ASTM A153Zinc Coating (Hot-Dip) on Iron and Steel Hardware.

A153M

c)Mill-galvanized (Pre-galvanized) Sheet

Galvanized steel sheet used to manufacture pre-galvanized channel or fittings shall be in accordance with the following standard:

ASTM A653/Steel Sheet, Zinc-Coated (Galvanized) by the Hot-Dip

A653MProcess.

Uncoated edges resulting from slitting, punching, and channel cut-off are permitted.

d)In-Line Hot Galvanized

Framing channel may be galvanized by applying a molten zinc coating as part of the continuous cold forming operation.

e)Mechanically Deposited Coatings

General fittings, accessories, and fasteners shall be mechanically coated in accordance with the following:

ASTM B695Coatings of Zinc Mechanically Deposited on Iron and Steel.

f)Other Metallic Coatings

Channel, general fittings, accessories, and fasteners may be coated with other metallic coatings to meet specific needs. Coatings shall be on surfaces that have been suitably prepared and cleaned. Procedures and coating thickness shall be to recognized standards or customer specifications.

4.1.2Non-Metallic Coatings

a)Painted Coatings

Paint may be of any type, including vinyl, vinyl-alkyd, epoxy, polyester, acrylic, amine, alkyd, etc.

Paint may be applied by any of the conventional processes including, but not limited to, spraying, brushing, dipping, flow-coating, roller-coating, powder-fusing, electro-depositing, etc. In all cases, the base metal shall be clean and properly prepared to bond with the paint coating.

Architectural finish or maintenance painting may be required.

Framing channel may be formed from prepainted coil or strip. In these cases, uncoated edges resulting from slitting, punching, and channel cut-off are permitted.

b)Anodized Coating

Aluminum channel and fittings, etc., that are anodized shall be coated in accordance with the Aluminum Association “Designation System for Aluminum Finishes AA-A21 Clear Coating Less Than 0.4 mils Thick”.

c)Other Non-Metallic Coatings

Polyvinylchloride (PVC), polyurethane, epoxy, polyester, and other nonmetallic coatings shall be applied by appropriate process to cleaned and prepared metals.

4.1.3Combination Coatings

Materials that have been metal-coated in accordance with Part 1 of this section may have additional non-metallic coating applied, e.g., galvanized material may be additionally PVC coated.

4.1.4Underwriters Laboratories Listed Items

All channel materials identified as “Listed by Underwriters Laboratories, Inc.” shall be finished to comply with UL5B “Standard for Strut-Type Channel Raceways and Fittings.”

SECTION 5

TOLERANCES

5.1CHANNEL, STEEL (ROLL-FORMED)

5.1.1Wall Thickness (information only)

a)Uncoated steel*

Manufacturer’s
Standard
Gage No. / Equivalent
Thickness,
Inches
20 / .0359
19 / .0418
18 / .0478
17 / .0538
16 / .0598
15 / .0673
14 / .0747
13 / .0897
12 / .1046
11 / .1196
10 / .1345

*See ASTM A568/A568M “Steel Sheet, Carbon and High-Strength Low-Alloy Hot-Rolled and Cold-Rolled, General Requirements,” for steel tolerances. Tolerances for Gages No. 10 through 16 are for Hot-Rolled Sheets and tolerances for Gages No. 17 through 20 are for Cold-Rolled Sheets.

b)Mill Galvanized Steel**

Manufacturer’s
Standard
Gage No. / Equivalent
Thickness,
Inches***
20 / .0374
19 / .0433
18 / .0493
17 / .0553
16 / .0613
15 / .0688
14 / .0762
13 / .0912
12 / .1060
11 / .1211
10 / .1360

**See ASTM A924/A924M “General Requirements for Steel Sheet, Zinc-Coated (galvanized) by the Hot-Dip Process.” Tolerances for Gages No. 10 through 16 are for Hot-Rolled Sheets and tolerances for Gages No. 17 through 20 are for Cold-Rolled Sheets.